MC68HLC908QY4 Datasheet, PDF (93/182 Pages) Motorola, Inc – Microcontrollers

FROM SIM
INTCLK
0
1
SIMOSCEN
EN
EXTERNAL RC
OSCILLATOR
RCCLK
Oscillator Module Signals
OSCRCOPT
TO SIM
TO SIM
BUSCLKX4
BUSCLKX2
÷2
1
0
PTA4
I/O
MCU
OSC1
PTA4/BUSCLKX4 (OSC2)
V_DD
R_EXT
See Chapter 16 Electrical Specifications
for component value requirements.
Figure 11-3. RC Oscillator External Connections
PTA4
OSC2EN
11.4 Oscillator Module Signals
The following paragraphs describe the signals that are inputs to and outputs from the oscillator module.
11.4.1 Crystal Amplifier Input Pin (OSC1)
The OSC1 pin is either an input to the crystal oscillator amplifier, an input to the RC oscillator circuit, or
an external clock source.
For the internal oscillator configuration, the OSC1 pin can assume other functions according to Table 1-3.
Function Priority in Shared Pins.
11.4.2 Crystal Amplifier Output Pin (OSC2/PTA4/BUSCLKX4)
For the XTAL oscillator device, the OSC2 pin is the crystal oscillator inverting amplifier output.
For the external clock option, the OSC2 pin is dedicated to the PTA4 I/O function. The OSC2EN bit has
no effect.
For the internal oscillator or RC oscillator options, the OSC2 pin can assume other functions according to
Table 1-3. Function Priority in Shared Pins, or the output of the oscillator clock (BUSCLKX4).
Table 11-1. OSC2 Pin Function
Option
XTAL oscillator
External clock
Internal oscillator
or
RC oscillator
OSC2 Pin Function
Inverting OSC1
PTA4 I/O
Controlled by OSC2EN bit in PTAPUE register
OSC2EN = 0: PTA4 I/O
OSC2EN = 1: BUSCLKX4 output
MC68HLC908QY/QT Family Data Sheet, Rev. 3
Freescale Semiconductor
93